Granaticins are polyketide-derived antibiotics produced as secondary metabolites by Streptomyces violaceoruber (James et al., J Gen Microbiol. 1989, 135(7), 1997-2003). Granaticins are benzoisochromanequinones (BIQs; Keller-Schierlein et al. Helv. Chim. Acta, 1968, 51, 1257-1268). Chemical modifications of granaticins have been carried out at C-10 via a C—C bond formation either by glycosylation or by dimerization (Hopwood, Chem Rev. 1997, 97, 2465-2497; Floss et al., J Nat Prod. 1986, 49, 951; Toral-Barza et al, Mol. Cancer Ther. 2007, 6, 3028-3038; Salaski et al., J. Med. Chem. 2009, 23, 2181-2184). Additional chemical or enzymatic modification can be made to 8,11-Ethanofuro[2,3-e]naphtho[2,3-c:6,7-c′]dipyran-2,6,13(9H)-trione, 3,3a,5,8,11,13b-hexahydro-7,8,12,15-tetrahydroxy-5,9-dimethyl-, (3aS,5S,8S,9R,11R,13bS,15R) of the 3-methyl-2-oxabicyclo[2.2.2]oct-5-ene-4,8-diol group of Granaticin A (e.g., coupling a carbohydrate moiety) provides granaticin B (Compound 1 in FIG. 10, also called MSK-777).
In addition to the anti-bacterial activity of granaticins, Frattini et al. has found that granaticins inhibit protein kinase pathways (Change et al., Antibiot. 1975, 28, 156; PCT Application Publication WO 2011/112635). In particular, granaticins were found to inhibit Cdc kinase activity based upon hits identified from high-thoroughput screening (HTS) of over 300,000 compounds for their ability to inhibit a heterodimer of a kinase (Cdc7) and an activator (Dbf4) that phosphorylates serine and threonine residues (WO 2011/112635).
Granaticin B was prepared from isolating the culture filtrate of Streptomyces lateritius or Streptomyces violaceoruber (Elson et al., J. Antibiotic, 1988, 41(4), 570-572; U.S. Pat. No. 3,836,642; Barcza et al., Helv. Chim. Acta, 1966, 4996), 1736-1740). The current process for preparing granaticin B involves down-stream or chemical unit operation to purify the natural product from fermentation (Keller-Schierlein, Helv. Chim. Acta., 1968, 51, 1257-1268; Gilpin, J. Antibiot., 1988, 41(4), 570-572). This process involves multiple steps including extractions and chromatography. The yield is not desirable, and degradation of the desired product has been observed. Therefore, there is a need to develop feasible a large-scale process for the production of granaticin B for clinical and research purposes.